Jimmy,
Beleive we've used both 80 & 100 foot for the trailing cone - best (most stable) length for a particular aircraft seems to vary a bit so we have an internal capstan with appropriate markings on the tubing & the FTE just runs it out as required before the testing starts.
Thanks for that. We used to reel the cone out but more recently it has been deployed to its full length on the runway. When the power increased the cone started to fly anyway.
Do you know if there different cone calibration corrections for different trail lengths?